1. Field of the Invention
This invention relates in general to electrically driven submersible well pumps, and in particular to a gas dissipation chamber for removing the gas processed by a through-tubing conveyed gas separator, thereby preventing such gas from entering the pump intake and gas locking the pump
2. Description of the Related Art
Most oil wells being pumped by a downhole electrical pump typically will also produce some gas. If the gas is of sufficient volume, it can reduce the performance of the pump. In these circumstances, gas separators are mounted in the assembly below the pump to separate gas from the well fluid entering the intake of the pump.
Typically, prior art gas separators utilize a rotatably driven rotor within a cylindrical housing. The rotor has at least one blade and often an inducer vane. The blade will impart a centrifugal force to the well fluid flowing through the housing. This centrifugal force tends to separate the liquid components from the gas components because of difference in densities, with the liquid components locating near the outer wall of the housing, and the gas remaining near the shaft.
A discharge member, mounted above the rotor, provides a passage from the central portion of the rotor to the exterior of the gas separator to discharge gas. The discharge member also provides a liquid passageway for the remaining portion of the well fluid to flow upward toward the intake of a pump. In most systems the pump is suspended on and discharges into the production tubing. The separated gas flows up the annular space in the casing surrounding the tubing.
In other types of installations, the pump assembly is lowered into and suspended within the production tubing. Preferably the motor is mounted to the lower end of the production tubing, and the pump assembly stabs into engagement with the drive shaft of the motor. The pump discharges into the production tubing. If a through tubing gas separator is desired, it would be lowered along with the pump assembly through the tubing. In such case, there would be very little clearance around the gas separator and the pump for the separated gas to dissipate up the tubing. Therefore a gas bubble could be created around the intake, causing a gas lock.
A gas dissipation chamber for through tubing conveyed ESP (electrical submersible pump) pumping system prevents gas discharged from the gas separator from entering the pump intake and subsequently gas locking the pump system. The gas dissipation chamber is installed in the string of tubing between the tubing crossover to the motor and the production tubing string. The gas dissipation chamber is a tubular device having a series of slots and ports and is located above the seal section and motor. The pump and a gas separator are lowered through the tubing and land in the gas dissipation chamber.
The gas dissipation chamber has a larger inner diameter than the production tubing to provide an annular flow area above the gas separator. Lower ports on the gas dissipation chamber allow the well fluid to enter the gas separator, while the gas discharged from the gas separator will flow up the annular flow area and be vented out through upper slots in the chamber, thereby permitting principally liquid to enter the pump. The gas dissipation chamber shunts the discharged gas from the gas separator and the pump intake, thereby preventing the gas locking of the pump system.